Pneumatic tool



Feh. 2,1926. 1,571,560

' W. A. SMITH ET AL PNEUMATIC TOOL Filed June 6, 1921 2 Sheets-Sheet 1 C C I C; I

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w. A. SMITH ET AL I PNEUMATIC TOOL Filed June 6, 1921 2 Sheets-Sheet? BY Cla re l rcefLloc 17mm WM WJVW 4457M ATTORNEYS Patented Feb. 2, 1926. v

UNITED STATES PATENT WILLIAM A. SMITH arm crannncn Doorman, or DETROIT, MICHIGAN, nssxenoas r0 cirrcaeornnumnric root COMPANY, or new YOR N; Y., a conrcaarron or ew JERSEY.

PNEUMATIC TOOL.

Application filed June 6,

1 To all whom it may can 01cm Be it known that we, WIL IAM A. SMITH and Cranmer H. 'DOQKHAM, both citizens of the United States of America, residing at-Detroit, in the county of WVayne and State of Michigan, have invented certain new and useful Improvements in Pneumatic Tools, of whichthe following is a specification, reference being had therein to the accompanying drawings.

The invention relates to pneumatic tools and similar fluid-operated devices and consists in the novel construction of the controlling valve as hereinafter set forth.

In the drawings:

Figure 1 is a longitudinal section through a pneumatic tool of our improved construction, showing the piston at the start of its working stroke;

Figure 2 is a similar view with the piston at the start of its return stroke;

Figures 3 and 4 are views similar to Figures l and 2 showing a modified construction.

A is the cylinder, B is the piston therein and C is the controlling valve. This valve is of spool form, being provided with the end heads C and G a central disk C of greater diameter, and annular chambers C and C between said disk and heads. D is the housing for the valve having a cylindrical bore of suflicient diameter for the passage of the central disk C and E and E are bushings within the casing which fit the end heads C and C and which are spaced from each other to receive the central disk C and to provide an air passage adjacent thereto. The casing D has a main air passage F surrounding the inner ends of the bushings and is further provided with channels G and H leading from chambers at opposite ends of the valve to opposite ends of the cylinder A. Between these end channels and the central air passage F are channels I and J, which are in constant communication respectively with the chambers C and C in the valve and with the cylinder adjacent to opposite ends thereof. K is an annular main exhaust passage arranged centrally of the cylinder A and adapted to be over-run by the piston B.

with the construction as described the central diskC is adapted to seat alternately upon the endsof the bushings E and E and 1921. serial No. 475,535.

when so seated, will cut on communication expose a larger area of the fluid pressure,

but this is reduced by tapering theends of the bushings so as to restrict the width of the seat and to permit a balancing pressure on the portion of the valve outside of said sea-t.

WVith the modified construction shown in Figs. 3 and 4, a different meansiifor shift'ing the valve is provided. This comprises a restricted passage Lconnecting the main air passageF with a chamber Mat one end of the valve, which end is reduced in. diameter as indicated at N. The opposite end ofthe valve, which is or larger diameter, is subjected to pressure in the chamber 0 connected by the passage P with the main air passage and by the passage Q, with the cylinder at a point on one side of the main exhaust channel K. The arrangement is such that a constant pressure will act upon the end N of the valve, while the pressure on the opposite end is alternately exhausted and built up by the sealing or unsealing of the channel Q by the piston. When the channel Q, is opened to the exhaust, the pressure upon the end N will shift the valve in one direction and as soon as the channel Q is sealed by the piston, the pressure in the chamber 0 will build up and the larger "area exposed to this pressure will overcome the pressure on the end N, shifting the valve in the opposite direction. The valve also controls auxiliary exhaust passages R and S, which are controlled by the opposite end heads Cand G and are alternately c0nnected with the chainbersC? With both of the construct-ions respectively illustrated in'Figures 1, 2 and 3, 4, the

center disk C will seat upon t'he en'd s oi? the bushings operating as a poppet valve,

while-the pressures upon the opposite ends of the valve are relatively varied to cause the shifting ofithe'samel The" amount of movement required is less than with a piston type valve and the positive "seating will prevent all leakage.

The complete cycle of operation in the construction as shown in Figures 1 and 2 is as follows: The piston and valve being in the positions shown in Figure l, the compressed air is admitted from the supply passage F to the chamber O of the valve to the left of the central disk C and through the channel I to the left-hand end of the cylinader. This will drive the piston B forward of the trapped air by the piston will raise the pressure which is communicated through the channel H to the right-hand end of the valve and through thechannel J to the chamber C thereby effecting the shifting of said valve into the, position shown. in Figure 2. Compressed air will then be admitted from the supply passage F through the chamber C at the right of the central disk C and through the channel J to thecylinderto the right of the-piston. This will drive the piston through its return stroke and after the exhaust channel K has been over-ridden, the exhaustingof the pressure in the channels H and J, together with the compression of the trapped air which is in communication with the channels G and I, will again shift the valve intothe position shown in Figure 1. v

In Figures 3 and 4 the cycle of operation is as follows :--The piston and valve being in the position shown in Figure 3 the compressed air is admitted from thesupply passage F through the restricted passage L to the chamber Msubjecting'the reduced end N to a continuous pressure and tending to force the same to the left. The compressed air is also admitted at the same time through the restricted passage P to the chamber 0 which communicates with the main exhaust channel K when the piston is in the position shown in Figure3. The main compressed air supply, however, is admitted from the pass F to the right of the central disk C when the valve is positioned, as shown in Figure 3, and through the enlarged passage to the right hand end of the cylinder: This i.

will drive the piston B forward todeliver the blow on the tool the air in advance of the piston being exhausted through the channel K. After the piston'has over-ridden the channel K- the drop in pressure occasioned by the exhausting of the air therethrough will lie communicated through. the channel on the right to the right hand side of the disk C The piston having moved to the position shown in Figure 4: has closed the passage from the chamber 0 and the air admitted through the passage P will act against the left hand end of the head G of the valve forcing the same to the right, opening the auxiliary exhaust port S which communicates with the chamber C and closing the auxiliary exhaust port R which communicates with the chamber 0. These auxiliary ports are controlled by the end heads C and C respectively of the valve and coact with the main exhaust in exhausting the air from the main chambers C and C as the valve is alternately seated. The reater pressure against the enlarged head 6' will overcome the resistance on the head N and assisted by the exhaust of air through the port K,-as described in connection with the cycle of operation of Figures 1 and 2 the valve will shift to the opposite position when the first operation described will take place.

l/Vhat we claim as our invention is:

1. A valve construction for fluid-operated motors comprising a cylindrical casing, bushings therein spaced to form an annularport therebetween, a spool valve having end heads slidably fitting said bushings, and a central head or disk extending into said annular port and alternatively seating upon the opposite ends of said bushings, channels, in said bushings surrounding said end headsand having exhaust ports connected thereto, said channels being sealed by said heads respectively when said disk is seated upon the opposite bushing, a fluid supply passage communicating with said annular port, channels in said bushings leading from said supply passage to chambers at theends of said valve, ports in said valve casing and bushing on opposite sides of said central disk alternatively in communication with said fluid. supply passage and leading to the motor controlled by said valve, and an exhaust passage for the chamber at one end of said valve.

2. The combination with a cylinder and a piston therein, of a controlling valve comprising a cylindrical casing, bushings in said casing spaced to form an annular port therebetween communicating with an air supply passage, a spool valve having end heads slidably fitting said bushings, and a central head or disk extending into said annular port and alternatively seated on the opposite ends of said' bushings, passages communicating with the annular chambers on opposite sides of said. disk and leading respectively to the opposite. ends of said cylinder, re-' stricted passages connecting said fluid supply. passage with chambers in said casing at opposite endsof said valve, 21 main exhaust port insaidlcylinder over-run by said piston, a valve exhaust port from the chamber at one end of said piston to said cylinder sealed by said piston when at one end of its stroke, and annular channels surrounding said end heads of the valve provided with auxiliary exhaust ports and respectively communicating with the spaces between said heads and central disk when the latter is seated on the opposite bushing.

3. The combination with a piston, of a cylinder having a main exhaust port overrun by said piston and valve-controlled supply passages leading to the opposite end of said cylinder, a controlling valve comprising a cylindrical casing having bushings therein spaced to form a central annular port therebetween communicating with the main fluid supply, said bushings having restricted channels therein leading from said main fluid supply to the opposite ends of the valve casing, being also ported on opposite sides of said annular port to communicate respectively with the passages to the opposite ends of said cylinder and being further provided with annular channels in their outer end portions communicating with auxiliary exhaust ports, and a spool valve within said valve casing having end heads slidably fitting said bushings, a central head or disk projecting into said annular port and alternatively seated on the opposite ends of said bushings, said end heads cooperating with said annular channels to alternatively open said auxiliary exhaust in each bushing when the disk is seated thereon,

4. A valve construction for fluid-operated motors comprising a cylindrical casing, bushings in said casing spaced from each other to provide an annular port therebetween communicating with the fluid pressure passage, longitudinal channels in said bushings extending from said fluid pressure passage to opposite ends of the casing and one of said bushings having an outer end portion of smaller diameter, a valve in said casing having end heads of different diameters slidably fitting within said bushings, and a valve-controlling exhaust passage communicating with the end of the casing having the head of larger diameter.

5. A valve construction for fluid-operated motors comprising a cylindrical casing, bushings therein spaced to form an annular port therebetween, the outer end of one of said bushings being reduced in diameter, a valve in said casing having end heads of different diameters slidably fitting said bushings, a central head or disk projecting into said annular port and alternatively seated on the opposite ends of the bushing, annular channels in said bushings connecting with exhaust ports and controlled respectively by said end head of large diameter and a head or disk adjacent to the head of small diameter, a restricted passage leading from the fluid supply passage to the small diameter end of the valve, a passage from said supply passage to the larger diameter end ofthe valve, and a valvecontrolling exhaust passage for said larger end of the valve.

6. A valve construction for a fluid-operated percussive tool comprising acylindrical valve casing having a central annular port providing opposed valve seats and end chambers differential in size, a valve having difierential end heads slidably fitting said chambers and a central head extending into said port for alternately engaging said valve seats, passages conducting live motive fluid to said end chambers whereby the end heads of the valve are continuously subjected to fluid pressure, and a passage extending from the larger of said end chambers under con trol of the piston of the tool for varying the continuous pressure in-said larger chamber.

In testimony whereof we affix our signatures.

WILLIAM A. SMITH.- CLARENCE H. DOOKHAM. 

